A CCD image sensor being an image pickup device that acquires a one-dimensional or two-dimensional image is constructed with a photodetecting section for which a plurality of pixels are arranged in an array form and a horizontal shift register inputted, in parallel, with electric charges from a plurality of vertical shift registers composing the photodetecting section. In such a configuration, electric charges generated in the respective pixels of the photodetecting section are transferred in the vertical direction by the vertical shift registers and are inputted to corresponding cells of the horizontal shift register. The horizontal shift register transfers the electric charges inputted from the vertical shift registers in the horizontal direction to be an output direction, and the electric charges are read out from an output end thereof.
Moreover, in order to speed up reading out of the electric charges generated in the photodetecting section, employed is a multi-tap structure for which the horizontal shift register is divided into a plurality of segmental shift registers and electric charge output ends are provided for the respective segmental shift registers. Such a configuration providing a plurality of output ends is useful particularly in such a case that the number of pixels in the photodetecting section is increased and a long time is required for reading out electric charges from all pixels with an ordinal configuration (see Patent Documents 1 and 2, for example).    Patent Document 1: Japanese Patent Application Laid-Open No. 2001-119010    Patent Document 2: Japanese Patent Application Laid-Open No. 2003-198954    Patent Document 3: Japanese Patent Application Laid-Open No. H08-18779